Model railroads have a long history of emulating trains and railroad systems throughout the world. Since the earliest model railroad and train systems have been developed, one of the primary goals of model railroaders has been to make the model train experience as realistic as possible for the user. A typical model train has a powered locomotive pulling a series of freight or passenger cars. A locomotive is typically powered by a DC or AC motor which drives one or more axels. The motor is driven by a power supply which applies voltage to the track from a transformer or other variable power source. The power source controls both the amplitude and polarity of voltage so that user may control both speed and direction of the train.
In addition to being able to control the speed and direction of a model train, systems were developed for operating a whistle or a bell located on the train. For example, in AC powered systems, this can be accomplished by applying a DC offset voltage superimposed on the AC voltage applied to the track. In other systems, the train has circuitry that distinguishes between the polarities of DC offset voltage. Thus, for example the whistle or horn would blow when a positive DC offset voltage is applied to the track and a bell would ring when a negative DC offset voltage is applied. These voltages are typically applied by pressing a button located on the power source to affect the desired sound.
More recently, systems have been developed for enhanced sound effects on locomotives in order to give the user a more realistic experience. One such example is marketed by MTH Electric Trains under the trade name Proto-Sound. The original Proto-Sound system offered a wide range of authentic locomotive sounds including: steam chuffing, diesel or electric engine sounds, bell, horn or whistle, locomotive startup and shutdown sounds, cab chatter, passenger station and freight yard sounds, squealing break sounds, air compressor sounds, and steam neutral sounds in addition to maintenance sound effects. This sound system along with lighting controls are typically controlled by a processor, which controls and drives the various component circuits located on the locomotive. The component circuits are located on a printed circuit board and include a light driver circuit, a sound driver circuit, and other driver circuits. Certain sounds for the model train may be stored in a flash memory which is connected to the processor. The processor is capable of retrieving one or more sound files from the flash memory, processing them, and outputting them to the sound system circuit. The sounds may also be stored alternatively on the same integrated circuit as the processor. The processor includes software for operating and processing the sounds. Power is required by the processor and memory in order to maintain, process, and output the sounds. For this purpose, the Proto-Sound system includes a rechargeable battery which provides power to the processor and memory when the track is powered down. Some of these rechargeable batteries take the form of a typical 9-volt battery. Power supply from the track through the power supply circuit during operating intervals serves to recharge the battery.
A problem exists in that these rechargeable batteries, after repeated use and/or long term storage, fail to maintain a proper charge. A low or discharged battery may result in improper shutdown of the sound system and malfunction of the processor. In some instances, improper shutdown may require factory authorized reprogramming to resolve the issues caused by a discharged battery. What is needed is an improved system which would minimize or otherwise alleviate the problems caused by discharged batteries in these locomotive sound systems.